Gamagrass, Tripsacum sp., is a polyploid, rhizomatous, perennial C4 grass closely related to corn (Zea mays L.) It has a base chromosome number x=18 and varying ploidy levels that range from 2n=36 to 2n=108. Tripsacum species are highly variable in form, vigor, and ecological adaptation. The endemic ranges for Tripsacum are from Canada to Chile. It is adapted to wide variation in elevations and habitats including swampy sites, deciduous forests, prairie, sandy soils, tropical forests, and near-desert conditions (Eubanks 2001).
This application describes a new gamagrass cultivar produced by crossing Eastern gamagrass, T. dactyloides L., with a recombinant plant that has genes from perennial teosinte (Zea diploperennis Iltis, Doebley and Guzman), maize (Zea mays L.), and gamagrass, (T. dactyloides).
Eastern gamagrass is a warm season perennial bunchgrass valued for its use as silage and hay for beef and dairy cows (van der Grinten et al. 2007). It has potential to produce large amounts of biomass in the southeastern United States. Some of its many desirable characteristics as an energy crop include high biomass yield potential, persistence, adaptation to different soil and climate conditions, non-invasiveness, carbon sequestration capacity, soil phytoremediation ability, and easy integration into existing farming operations (Douglas 2000; Grabowski et al. 2004; Hinchman et al., 1999; Mashingo et al. 2008; van der Grinten 2007; Weimer and Springer 2007). Gamagrass yields of up to 24,965 kg/ha (Owsley 2008) are comparable to those of switchgrass and bermudagrass (Parrish and Fike 2005; Hill et al. 1993).
Diploid perennial teosinte, Zea diploperennis Iltis, Doebley and Guzman (hereafter referred to as diploperennis), is a wild relative of corn that was unknown until it was discovered on the threshold of extinction in the mountains of Jalisco, Mexico in the late 1970's (ltis et al. 1979). It is in the same genus as corn, has the same chromosome number (2n=20), and hybridizes easily with corn. Crosses between corn and Eastern gamagrass generally produce hybrids that are male sterile and essentially female sterile. Early attempts to cross Tripsacum and the wild Zeas referred to as teosinte, failed (Mangelsdorf 1974). In 1985, Eubanks recovered viable, fertile hybrids from crosses between diploperennis and Eastern gamagrass and (Eubanks 1989, 1992, 1996, 2007). These gamagrass-teosinte recombinants are cross fertile with corn, teosinte, and gamagrass.
The new plant is a gamagrass cultivar introgressed with Zea genes by crossing a Tripsacum dactyloides L. plant (referred to as ‘Eagle Point’), with ‘7022*Devil Corn’, a plant produced by pollinating the silks of a corn-Tripsacorn hybrid (referred to as ‘7022’), with pollen from a gamagrass-diploperennis recombinant (referred to as ‘Devil Corn’).
On Jul. 24, 2003, Eubanks pollinated ‘Eagle Point’ Tripsacum dactyloides with pollen from ‘7022*Devil Corn’. The seed germinated in a petri dish Nov. 24, 2003, was placed in pot in potting soil Dec. 4, 2003, and grown in a greenhouse in Durham, N.C. The seedling developed into a normal, fully fertile plant that is perennial and produces viable fruits year-round in the greenhouse. The plants have been propagated by rhizome divisions and planted in Durham, N.C., Lumberton, Miss., and Austin, Tex., where they have been continuously maintained in outdoor nurseries. This new Tripsacum-Zea recombinant expands the genetic diversity for crosses between Tripsacum and Zea via conventional hand pollination technique. It enhances the link between the wild relatives and modern corn, which promises to be beneficial in corn improvement breeding programs. Unique propagation of this plant through successive generations by means of rhizome divisions has demonstrated that the new plant not only retains continuous and abundant production capability, but also has distinguishing characteristics that hold true from generation to generation and appear to be firmly fixed.
Examination of the roots revealed that ‘Eagle Point Devil Corn’ (referred to hereafter as EPDC) has well developed air passages, referred to as aerenchyma, in its roots. This property provides oxygen to roots enabling them to survive anaerobic conditions as in flooded soils (Comis 2005). It also allows the roots to grow deep below the hardpan. This deep-rooting characteristic conveys outstanding drought tolerance. The plant tolerates acid soil and aluminum, making it a good candidate for phytoremediation of contaminated soils and wastewater (Eubanks 2006; Hinchman et al. 1999).
EPDC plants exhibited exceptional drought and heat tolerance in 2011 in the Tripsacum nursery at the Brackenridge Field Laboratory, Austin, Tex. In 2011, Central Texas experienced exceptional (D4) drought, the most severe ranking by the National Drought Mitigation Center (Walsh 2011). It was the worst one-year drought on record. With just 6.5 in (17 cm) of rain since November 2010, the 2011 growing season began with a 27.5 in (68.7 cm) water deficit. Texas also experienced record-shattering heat in 2011 with 90 days of temperatures from 100° F. (37° C.) to 112° F. (44.4° C.). EPDC plants survived the drought and heat without supplemental water from June to August.
Chemical analysis revealed EPDC has higher carbohydrate and sugar content than its gamagrass parent. The EPDC total carbohydrates (lignin, ash, glucan and xylan) are 94.1 percent of biomass dry weight. This exceeds its gamagrass parent by 13%. Due to its high carbohydrate content and higher carbohydrate conversion (83.8%), EPDC produces higher sugar yields. Glucose is 410.1 mg m−1 raw biomass, xylose is 169.5 mg m−1 raw biomass, and total sugars are 595.8 mg m−1 raw biomass. The EPDC sugar yield is 51.6% greater than switchgrass, a prevalent biofuel feedstock.
EPDC Propagation has taken place in Durham, N.C., Lumberton, Miss., and Austin, Tex.